1. Field of the Invention
The present invention relates generally to a signal transmitting system and method in a mobile communication system, and in particular, to a system and method for transmitting a signal using a Multi-Mode Power Amplifier (MMPA) in a communication system.
2. Description of the Related Art
Provisioning of services having a variety of Quality of Service (QoS) levels at a high rate is an active study area for future-generation communication systems. Particularly, studies are actively being conducted on provisioning of high-speed services with mobility and QoS guaranteed in Broadband Wireless Access (BWA) systems including Wireless Local Area Network (WLAN) and Metropolitan Area Network (MAN), for future-generation communications. In this context, the 4th Generation (4G) mobile communication system is being developed toward the use of multiple carriers for high-speed service while guaranteeing mobility and QoS.
Regarding a signal transmitting system in a typical communication system, there are two types of signal transmitting systems: one uses a Single Carrier Power Amplifier (SCPA) and the other uses a Multi-Carrier Power Amplifier (MCPA). Both kinds of signal transmitting systems may use a single Frequency Assignment (FA) or multiple FAs. With reference to FIG. 1, the structure of an SCPA-type signal transmitting system using a single FA will be described.
FIG. 1 is a block diagram of an SCPA-using signal transmitting system operating under a single FA in a typical communication system. Referring to FIG. 1, the signal transmitting system includes a Single-FA input Signal Generation Block (SGB) 111, an SCPA 113, a Front-End Block (FEB) 115, and an antenna (ANT) 117.
For the input of an information signal to be transmitted, the SGB 111 generates a single FA input signal corresponding to a single FA, f1. The SCPA 113 amplifies the single FA signal f1 by a predetermined gain. The FEB 115 performs Radio Frequency (RF) preprocessing on the amplified signal and sends the RF preprocessed signal through the ANT 117.
The signal transmitting system, which operates using a single FA as illustrated in FIG. 1, may also use multiple FAs, which will be described below.
FIG. 2 is a block diagram of an SCPA-type signal transmitting system operating under multiple FAs in the typical communication system.
It is assumed herein that the signal transmitting system uses N FAs, f1 to fN. Referring to FIG. 2, the signal transmitting system includes N SGBs 211-1 to 211-N, N SCPAs 213-1 to 213-N, a Channel Combiner Block (CCB) 215, an FEB 217, and an ANT 219.
Information signals to be transmitted by the respective FAs are provided to corresponding SGBs. Specifically, an information signal for f1 is provided to the SGB 211-1 and in the same manner, an information signal for fN is provided to the SGB 211-N.
For the input of the information signal, the SGB 211-1 generates a single FA input signal corresponding to f1. In the same manner, the SGB 211-N generates a single FA input signal corresponding to fN, for the input of the corresponding information signal. The SCPA 213-1 amplifies the single FA signal received form the SGB 211-1 by a predetermined gain and in the same manner, the SCPA 213-N amplifies the single FA signal received form the SGB 211-N by a predetermined gain.
The CCB 215 channel-combines the amplified signals received from the SCPAs 213-1 to 213-N. The FEB 217 RF-preprocesses the combined signal and sends the preprocessed signal through the ANT 219.
Because the CCB 215 suffers a significant insertion loss, channel-combining of adjacent FAs is very difficult. Therefore, in case where multi-FAs are used, the SCPAs 213-1 to 213-N are designed to have a higher gain due to the insertion loss, for ensuring the same transmit power as that of a signal transmitted from the ANT in the SCPA-using signal transmitting system operating with a single FA. That is, the gain of the SCPAs 213-1 to 213-N must be increased due to the insertion loss, compared to the use of an MCPA.
Consequently, when the SCPA-type signal transmitting system uses more FAs, it is equipped with as many SCPAs as the number of the FAs. Considering the antenna transmit power, more power is consumed due to the insertion loss of the CCB 215, compared to the case of using an MCPA. The resulting requirement of cooling capacity in the signal transmitting system increases the overall system operation cost.
With reference to FIG. 3, a description will be made of the structure of an MCPA-type signal transmitting system operating with a single FA. FIG. 3 is a block diagram of an MCPA-type signal transmitting system operating under a single FA in the typical communication system. Referring to FIG. 3, the signal transmitting system includes an SGB 311, an MCPA 313, an FEB 315, and an ANT 317.
For the input of an information signal to be transmitted, the SGB 311 generates a single FA input signal corresponding to a single FA, f1. The MCPA 313 amplifies the single FA signal f1 by a predetermined gain. The FEB 315 performs RF preprocessing on the amplified signal and sends the RF preprocessed signal through the ANT 317.
While it can amplify in the single FA case as illustrated in FIG. 3, the MCPA 313 is optimized for multi-FA amplification. Therefore, the operation of the MCPA 313 with the single FA leads to unnecessary power consumption. In addition, since the MCPA 313 is expensive relative to an SCPA, the initial installation cost of the whole system is increased.
FIG. 4 is a block diagram of an MCPA-type signal transmitting system operating under multiple FAs in the typical communication system.
It is assumed herein that the signal transmitting system uses N FAs, f1 to fN. Referring to FIG. 4, the signal transmitting system includes N SGBs 411-1 to 411-N, an FA Combiner Block (FCB) 413, an MCPA 415, an FEB 417, and an ANT 419.
Information signals to be transmitted by the respective FAs are provided to corresponding SGBs. Specifically, an information signal for f1 is provided to the SGB 411-1 and in the same manner, an information signal for fN is provided to the SGB 411-N.
For the input of the information signal, the SGB 411-1 generates a single FA input signal corresponding to f1. In the same manner, the SB 411-N generates a single FA input signal corresponding to fN, for the input of the corresponding information signal. The FCB 413 FA-combines the N single FA signals received from the SGBs 411-1 to 411-N, thereby creating a multi-FA signal.
The MCPA 415 amplifies the multi-FA signal received from the FCB 413 by a predetermined gain. The FEB 417 RF-preprocesses the amplified signal and sends the preprocessed signal through the ANT 419.
Compared to the use of the SCPA, the use of the MCPA obviates the need for a CCB even in the case of using multiple FAs. Therefore, a power consumption increase caused by the insertion loss of the CCB is avoided. However, the manufacturing cost of the MCPA is typically higher than that of the SCPA. In addition, when a small number of FAs are used, the capacity of the MCPA is only partially utilized, thereby unnecessarily increasing the initial installation cost of the system. If an SCPA operates under too a small number of FAs to need a CCB, the signal transmitting system using the MCPA is less efficient than that using the SCPA in terms of structural complexity.